OFFSET
1,1
COMMENTS
Primes p such that 2*p+7 and 4*p+21 are also primes. - Vincenzo Librandi, Aug 04 2010
LINKS
John Cerkan, Table of n, a(n) for n = 1..10000
FORMULA
a(n) == 5 (mod 6), for n > 1. - John Cerkan, Sep 12 2016
MATHEMATICA
Select[Prime@ Range[10^3], Times @@ Boole@ PrimeQ@ NestList[2 # + 7 &, #, 2] > 0 &] (* Michael De Vlieger, Sep 12 2016 *)
PROG
(Magma) [n: n in [0..100000] | IsPrime(n) and IsPrime(2*n+7) and IsPrime(4*n+21)] // Vincenzo Librandi, Aug 04 2010
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved